We will continue to explore the enzymatic mechanisms whereby malignant cells break down host connective tissue structures. The invasive behavior of the malignant rabbit V2 carcinoma and the properties of collagenase produced by this tumor when implanted in rabbit or nude mouse have been the main theme of our studies for the last two years. The cellular source, properties and regulation of collagenase in particular, and other neutral proteases, in V2 carcinoma will be explored by specifically focussing on 1) interactions between host and tumor cells; 2) local tissue and circulating inhibitors and 3) the fine structural aspects of connective tissue degradation. Antibody will be prepared against purified rabbit tumor and mouse bone collagenase for identification of the enzyme present in rabbit V2 carcinoma implanted in nude mouse and media of mixed culture of V2 cells and nude mouse skin fibroblasts. The collagenase inhibitor isolated from rabbit tumor tissue will be purified, its properties, mechanism of inhibition of tumor collagenase and possible relationship to fibronectin (another collagenase inhibitor) will be further explored. Antibody will be prepared against purified inhibitor to be used for studies on tissue localization and distribution of the inhibitor under normal and pathological states. V2 carcinoma will be implanted in rabbit cornea and its invasive and destructive behavior at different stages of growth relative to vascularization will be studied by electron microscopy, and also the distribution of collagenase by immunofluorescence.